Scarlett Volcanic Member: Difference between revisions
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Scarlett Volcanic Member (SCV), Carboniferous, Midland Valley of Scotland
Scarlett Volcanic Member is part of the Bowland Shale Formation
Name
From Scarlett Point, Isle of Man. Previous names include the Scarlett Volcanic Series of Lewis (1930)[1] and the Scarlett Volcanic Formation of Dickson et al. (1987)[2]. The present definition is that of Chadwick et al. (2001)[3]. See also Lamplugh (1903)[4].
Lithology
The member is dominated by submarine volcaniclastic debris flows and gravity slides. Olistoliths of older Tournaisian and/or Visean carbonates and claystone rafts also occur, as do isolated vesicular basaltic clasts.
Genetic interpretation
The tuffs are waterlain, the volcaniclastic debris flows and gravity slides are submarine.
Stratotype
A partial type section (a strike section through the member) comprises largely continuous coastal outcrops from Scarlett Point (SC 2570 6610) to Close-ny-Clollagh Point (SC 2450 6710). Here the sharp base of the member is succeeded by submarine volcaniclastic rocks (including debris flows, gravity slides and pillow lavas) with entrained claystone rafts and megaclasts. The section is no more than 50 m thick and the top of the member is not seen (see Dickson et al., 1987, pp. 219–223[2]; Chadwick et al., 2001, p. 63[3]).
Lower and upper boundaries
The base is clearly seen on the foreshore below Close-ny-Chollagh Point (SC 245 671) where volcaniclastic rocks rest with a sharp, baked contact on underlying dark claystones of the Bowland Shale Formation (Figure 8, Column 8).
The top of the member is not exposed, so the nature of the upper boundary is unknown.
Thickness
Some 50 m. The thickness of the member is difficult to estimate due to the numerous olistoliths and rolling dips present in the outcrop.
Distribution and regional correlation
Southern part of the Isle of Man, in the Castletown area, from Scarlett Point (SC 257 661) to Close-ny-Clollagh Point (SC 245 671). Visean rocks in the northern part of the island are entirely concealed and hence it is unknown whether it is present in the north. Well 112/19-1, just off the north-east of the Isle of Man proved 198 m of Brigantian to Pendleian strata and no volcanic successions, so the member is likely to be absent in the northern part of the island.
Age
Brigantian.
References
- ↑ Lewis, H P.1930.The Avonian succession in the south of the Isle of Man.Quarterly Journal of the Geological Society of London, Vol. 86, 234–290.
- ↑ 2.0 2.1 ickson, J A D, Ford, T D, and Swift, A.1987.The strati-graphy of the Carboniferous rocks around Castletown, Isle of Man.Proceedings of the Yorkshire Geological Society, Vol. 46, 203–229.
- ↑ 3.0 3.1 Chadwick, R A, Jackson, D I, Barnes, R P, Kimbell, G S, Johnson, H, Chiverrell, R C, Thomas, G S P, Jones, N S, Riley, N J, Pickett, E A, Young, B, Holliday, D W, Ball, D F, Molyneux, S G, Long, D, Power, G M, and Roberts, D H.2001.The geology of the Isle of Man and its offshore area.British Geological Survey Research Report, RR/01/06
- ↑ Lamplugh, G W.1903.The geology of the Isle of Man.Memoir of the Geological Survey of Great Britain.